This invention is directed to magnetic bubble (domain) devices and, more particularly, to a new and improved passive annhilator for bubble memory chips.
Magnetic bubble domain devices (chips) are now well-known in the art. These chips have means for forming and supporting bubbles under a suitable bias field and for propagating bubbles on patterns of propagate elments serially, as a stream, in response to an in-plane rotating magnetic field. The use of gating devices which transfer bubbles from one path to another path in response to a current applied to a control gate conductor associated with the gate is also old.
In the bubble memory storage area, identical closed storage loops are formed of a selected type of propagate elements and are connected by suitable input tracks of propagate elements from a bubble generator and an output track of propagate elements to a bubble detector which senses the presence or absence of a bubble in the detector and sends an appropriate signal to a utilization device. The presence or absence of a bubble on the individual propagate elements represents information stored in memory and read out by the detector. A bubble transferred into a storage loop will circulate indefinitely in response to the rotating in-plane magnetic field unless transferred out and, a suitable bias source, control circuits, etc. for the application of pulse to the functional elements mentioned above such as transfer-in and transfer-out gates are, of course, well-known.
Also well-known are transfer-in and transfer-out gates and decoding gates for decoding information to be sent to the storage loops on the bubble memory chip. Too, bubble memory chips are conventionally provided with annihilators to rid the system of unwanted bubbles. These annihilators are either of an active type which requires a current conductor line associated therewith to be pulsed to annihilate the bubble, or of a passive type, which does not have a conductor associated therewith. Also, the annihilator may be a guard rail located so that unwanted bubbles will be confined therein and eventually destroyed. A typical example of a passive annihilator is shown in FIG. 1 where a rectangular element 10 of permalloy material (like the propagate elements 12 connected thereto) with a protrusion 14 arranged in the path of bubble propagation such that a bubble moving along the path to the annihilator element 10 is attracted to the protrusion 14 and carried off onto the rectangle 10 where it will continue to rotate about the periphery of the rectangle. As an additional new bubble reaches the rectangle, the one rotating thereon, would be collapsed. However, at a low magnetic bias field this type of annihilator element generally results in bubbles being transferred (kicked) off the annihilator element during the cycle after a new bubble has entered onto the rectangle 10. Thus, the prior art passive annihilator is not reliable at low bias field conditions and it is a primary object of this invention to provide a passive annihilator in which bubbles do not escape the annihilator whether under low or high bias field conditions.